CN110943461A - Intelligent integrated power distribution device applied to low-voltage transformer area and method thereof - Google Patents
Intelligent integrated power distribution device applied to low-voltage transformer area and method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
- H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
- H02J3/1864—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein the stepless control of reactive power is obtained by at least one reactive element connected in series with a semiconductor switch
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/10—Flexible AC transmission systems [FACTS]
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a device and a method for reactive compensation and three-phase imbalance mixed compensation of a distribution network area. The invention can solve various problems of other compensation devices in the market, not only adjusts the three-phase load unbalance, but also dynamically, bidirectionally and continuously adjusts the reactive power; the control unit of the SVG is used for switching the intelligent capacitor preferentially, so that the control precision and speed are improved; the SVG is used for fine compensation, so that the compensation precision is improved, frequent switching of the intelligent capacitor is avoided, and the service life of the capacitor is prolonged; the intelligent capacitor is complementary with the SVG, can be applied to high-power occasions, reduces the system volume and reduces the system cost.
Description
Technical Field
The invention relates to the field of power supply and distribution, in particular to an intelligent comprehensive power distribution device and method applied to a low-voltage transformer area.
Background
A low voltage block refers to an area of low voltage (0.4kV) supply affected by 35(10) kV/0.4kV distribution transformers. The power consumption of the transformer area is generally the power consumption of residents, and the quality of the power consumption is high and low, so that the lives of the residents are directly influenced. Meanwhile, more and more distributed power supplies are connected to the power distribution network, and the problems of voltage deviation, three-phase imbalance, abnormal check point power factor and other electric energy quality are brought to the power distribution network. When the system is in a three-phase unbalanced state, the negative sequence component may cause the problems of false operation of a relay protection device, additional power loss generated by negative sequence and zero sequence current, zero drift of a neutral point and the like to equipment in the system, and finally the economy of the system is reduced and the safety of the system is threatened.
In order to effectively solve the above problems, the most common method at present is to use a reactive power compensation device with split-phase control for compensation. The reactive power compensation device can reduce active loss, improve the output of the transformer and the utilization rate of the transformer, improve the power factor of power consumption of a low-voltage distribution network system and the electric energy quality of the power consumption of the low-voltage distribution network system, and effectively improve the conditions of three-phase imbalance and terminal voltage drop of the system.
At present, the most common reactive power compensation devices mainly comprise three types, namely a parallel capacitor/reactor, a static reactive power compensator and a static reactive power generator, wherein the parallel capacitor/inductor is used for realizing reactive power compensation by connecting capacitors/inductors in series and in parallel in a power grid, and the defects are that the compensation capacity can not be continuously and smoothly adjusted, voltage drop can be increased, even additional active loss can be generated, and the inductor can increase the volume and the weight.
A Static Var Compensator (SVC) is a FACTS device in which a reactor with controllable inductance and a capacitor bank whose capacitance can be changed in steps are connected in parallel, and compensation capacitance can be changed smoothly. The method has low cost and reliable work, but only can compensate in stages, has poor precision, is easy to cause under-compensation or over-compensation, has poor following performance, cannot adapt to occasions with fast load change, and cannot inhibit flicker and unbalance.
The Static Var Generator (SVG) adopts a self-changing phase-changing current technology, and realizes the rapid dynamic regulation of reactive power by regulating the amplitude and phase of output voltage/current at an alternating current side. The method has the advantages of high regulation speed, wide operation range, no need of energy storage elements such as large-capacity capacitors and the like, and capability of inhibiting harmonic waves in the compensation current. However, the structure is complicated when the capacity is large, the technical requirement is high, and the cost is high.
In summary, some common reactive power compensation devices in the market currently cannot compensate the reactive power of the system while adjusting the three-phase imbalance, most of the reactive power compensation devices are discontinuously adjusted, and if continuous adjustment is to be achieved, the size of the system is increased, and the cost is very high.
There is therefore a need for more efficient and accurate reactive power compensation apparatus and techniques that simultaneously provide continuous, stable, accurate three-phase imbalance regulation and reactive power compensation without affecting the load operation, and that reduce the overall size and cost of the system.
Disclosure of Invention
In order to solve the problems, the invention provides an intelligent comprehensive power distribution device applied to a low-voltage transformer area, which is connected in parallel to a power supply busbar of a power distribution network, and comprises an SVG, an intelligent capacitor bank, other switching circuits and a control loop, wherein the SVG, the intelligent capacitor bank and the other switching circuits are used for carrying out hybrid compensation on three-phase imbalance and reactive power of the power distribution network, so that the power quality of the power distribution network is improved, and the system cost is reduced.
Preferably, the SVG is connected in parallel to a power supply bus bar of the power distribution network, so that three-phase load imbalance can be adjusted, and meanwhile, reactive power can be dynamically, bidirectionally and continuously adjusted; the intelligent capacitor bank is connected in parallel to the power supply busbar of the power distribution network, so that three-phase load imbalance can be adjusted, and reactive power is compensated; and the SVG and the intelligent capacitor cooperate to jointly complete reactive compensation of the three-phase unbalanced load.
Preferably, the SVG adopts a modular design, the topology of the SVG is three levels, the module can contain a soft power-on circuit, an energy storage unit, a filter circuit, a detection circuit, an IGBT power conversion unit, a driving circuit, a tracking control circuit, an auxiliary power system, a monitoring display liquid crystal screen and other units, and the energy storage unit adopts a capacitive or inductive element.
Preferably, the intelligent capacitor bank is composed of a plurality of groups of intelligent capacitors, and the intelligent capacitor bank can be composed of a plurality of capacitor combinations of co-compensation and sub-compensation. Each intelligent capacitor consists of a switching switch module and a capacitor group, wherein the switching switch module consists of a thyristor, a magnetic latching relay, a zero-crossing trigger conduction circuit and a thyristor protection circuit, so that zero switching of the capacitor is realized, and inrush current impact and operation overvoltage are avoided in the switching process. The switch module has high action response speed and can be frequently operated.
Preferably, the SVG controller controls the break-make of intelligent condenser simultaneously, carries out the communication through the RS485 interface between the two, through SVG control chip, controls intelligent condenser switching, and the priority control intelligent condenser carries out the switching compensation, adopts SVG to carry out essence benefit and unbalanced three phase compensation afterwards.
The invention also provides a method for realizing reactive compensation of three-phase unbalanced load by using the device, which is characterized by comprising the following steps: the system collects the voltage and current signals of the power grid and the load end in real time through the sensor, transmits the signals to the DSP through the signal conditioning circuit, performs reactive current calculation and reactive power distribution, obtains the switching scheme and SVG current control instructions of the intelligent capacitors, transmits the instructions to each intelligent capacitor through RS485 communication, controls the on-off of the capacitors, generates PWM control signals to drive the IGBTs in the SVG module, and finally completes reactive power compensation of three-phase unbalanced load through the cooperation of the two.
Preferably, the device passes through SVG internal control ware control intelligent electric capacity, realizes the reactive compensation to unbalanced three phase load, specifically includes the following step:
(1) collecting system alternating current, sending the conditioned system alternating current to a DSP (digital signal processor) for coordinate transformation, decomposing to obtain three-phase fundamental wave positive sequence active current and other current components including the sum of harmonic wave, fundamental wave reactive current and fundamental wave negative sequence current, and separating reactive current; calculating the average current and obtaining the reactive current to be compensated;
(2) calculating the type and the number of intelligent capacitors to be switched according to a reactive power distribution principle, and controlling the on-off of thyristors of the corresponding intelligent capacitors in an RS485 communication mode to realize the switching of the intelligent capacitors;
(3) the intelligent capacitor also detects voltage and current signals of a power grid, collected data are calculated and analyzed to judge whether faults such as overcurrent, overvoltage and overheating occur, the working capacitor is cut off in time, and a main circuit is protected.
Preferably, SVG is controlled through DSP in the device, realizes the reactive compensation to three-phase unbalanced load, specifically includes the following step:
(1) collecting the voltage of a direct current bus of the system, sending the voltage into a DSP (digital signal processor) for conditioning, then carrying out PI (proportional integral) conditioning on the voltage and a reference value, and finally superposing the voltage and the reference value to a current detection instruction signal to finally realize the stable adjustment of the direct current bus;
(2) calculating a reactive current value needing SVG compensation by combining the reactive current component obtained by sampling calculation and the compensated reactive current of the intelligent capacitor;
(3) setting the SVG current compensation quantity to be opposite in polarity and equal in magnitude to the reactive current value to be compensated of the SVG, and controlling the total reactive current to be 0 by the compensation quantity and the reactive current component through a current regulator;
(4) and intersecting the output of the current regulator and the output of the triangular wave generator to obtain a PWM driving signal, and driving the corresponding IGBT module through the isolation amplifier.
The invention has the following advantages:
(1) the invention provides an intelligent comprehensive power distribution device and method applied to a low-voltage transformer area, which can effectively improve the three-phase imbalance condition of a power grid, improve the power factor of the power grid and optimize the electric energy quality of the power distribution network.
(2) According to the invention, the controller in the SVG controls the SVG unit and the intelligent capacitor bank to work coordinately, and when the system needs compensation, the intelligent capacitor bank is switched preferentially, so that reactive power optimal distribution is realized, and the purposes of continuous compensation and system cost reduction are achieved.
(3) The intelligent capacitor bank is coordinated and controlled by a controller part of the SVG, the capacitor is switched according to the three-phase imbalance and reactive power distribution principle, and the compensation capacitor is quickly and stably switched in or switched out in a contactless manner by the thyristor in the capacitor.
(4) The SVG part of the invention adopts a power electronic device to carry out hybrid compensation, and the power electronic device adopts a quick switching device, so that the system response speed is high and the control precision is high. Meanwhile, the SVG can flexibly compensate the residual compensation capacity of the intelligent capacitor, so that frequent switching of the capacitor is avoided, and the service life of the capacitor is prolonged.
(5) The device is installed on a power distribution network busbar and connected with a system load in parallel, the connection mode is simple, the device can be quickly cut off when in fault, the work of an original system cannot be influenced, and the device is safe and reliable.
Drawings
FIG. 1 is a block diagram of an embodiment of an intelligent integrated power distribution apparatus and method for a low voltage substation area;
FIG. 2 is a graph showing the operating characteristics of the apparatus of the present invention for three-phase imbalance regulation and reactive hybrid compensation;
FIG. 3 shows a schematic diagram of the apparatus of the present invention for three-phase imbalance regulation and reactive hybrid compensation;
FIG. 4 shows a topological structure diagram of an SVG main circuit based on a three-level technology in the device of the present invention;
FIG. 5 shows an SVG equivalent circuit diagram and a vector diagram in the device of the present invention;
fig. 6 shows a power decoupling equivalent control block diagram of three-level SVG in the apparatus of the present invention.
Detailed Description
Fig. 1 is a diagram showing a structure of an embodiment of an intelligent integrated power distribution device and a method thereof applied to a low-voltage transformer area, the device of the embodiment includes an SVG, an intelligent capacitor bank and other switching circuits, a control loop and a communication loop, the SVG is connected in parallel to a power supply bus of a power distribution network, so as to adjust three-phase load imbalance and dynamically, bidirectionally and continuously adjust reactive power; the intelligent capacitor bank is connected in parallel to the power supply busbar of the power distribution network, so that three-phase load imbalance can be adjusted, and reactive power is compensated; SVG and intelligent capacitor coordinate and cooperate, accomplish the reactive compensation of unbalanced three phase load jointly to improve distribution network electric energy quality, reduce system cost.
As shown in fig. 1, the intelligent integrated power distribution device detects the voltage and current of the power grid and the current signal of the load side in real time through a voltage and current sensor, calculates the power factor and the reactive current of the system, and calculates in real time to obtain the total reactive capacity to be compensated; then, controlling the switching of each compensation branch according to the three-phase imbalance and reactive power distribution principle, preferentially calculating the type and the number of intelligent capacitors to be switched, and controlling the switching of the intelligent capacitors in an RS485 communication mode; and meanwhile, the inductive or capacitive reactive power of the SVG to be compensated is calculated, and the SVG is controlled to achieve accurate reactive power compensation, so that the reactive power compensation of the whole system is realized.
The intelligent capacitor detects voltage and current signals of a power grid at the same time, collected data are calculated and analyzed, whether faults such as overcurrent, overvoltage and overheating occur or not is judged, the working capacitor is cut off in time, and a main circuit is protected. The SVG also has a protection program, judges faults of overvoltage/undervoltage, overcurrent, open circuit, overtemperature and the like of the system by detecting information of voltage, current, temperature and the like of the system in real time, and timely cuts off the SVG from the system.
Fig. 2 shows the operating characteristics of the device according to the invention for three-phase imbalance regulation and reactive hybrid compensation. In the hybrid reactive compensation system, the SVG and a plurality of groups of intelligent capacitors jointly complete reactive compensation, the total reactive Q required to be compensated by the system is mainly compensated by the intelligent capacitors, but the intelligent capacitors can only complete graded compensation, reactive compensation between grades is required to be further completed through the SVG, and finally reactive accurate compensation is realized. Meanwhile, within the compensation capacity range of the SVG, the SVG is used for compensation, and the switching times of the intelligent capacitor are reduced as much as possible.
Fig. 3 shows a schematic diagram of the device according to the invention for three-phase imbalance regulation and reactive hybrid compensation. The system collects alternating current through a sampling unit, and sends the alternating current to a DSP (digital signal processor) for calculation and coordinate transformation after conditioning, so as to judge whether the system is in a three-phase unbalanced state and calculate reactive current; calculating the type and the number of intelligent capacitors to be switched according to a three-phase unbalance compensation principle and a reactive power distribution principle, and controlling switching units of the corresponding intelligent capacitors in an RS485 communication mode, namely switching on and off of thyristors, so as to realize switching of the intelligent capacitors; and meanwhile, calculating reactive components to be compensated of the SVG unit, and controlling the on-off of the SVG main loop.
Fig. 4 shows a SVG main circuit topology structure based on a three-level technology, and compared with a two-level converter, each IGBT only bears half of the total voltage of a direct current side in the phase change process of the three-level converter, so that the capacity of equipment is improved, the cost is reduced, and the SVG main circuit topology structure has the advantages of low output voltage, low current harmonic, small electromagnetic interference and the like.
Fig. 5 shows an SVG equivalent circuit diagram and a vector diagram, where Lc, Rc are the equivalent inductance and resistance of the SVG system (including the connecting reactor and the impedance of the system itself), Us is the grid-side voltage, Uc is the SVG output voltage, and Ic is the current absorbed by SVG. Analyzing the SVG equivalent circuit shown in fig. 5(a), SVG can be treated as a voltage control current source, and the phase and amplitude of the current Ic absorbed by SVG from the power grid are indirectly controlled by changing the phase difference between the output voltage Uc of SVG and the power grid voltage Us and the amplitude of Uc, that is, whether the SVG absorbs capacitive reactive power or inductive reactive power, and the magnitude of the reactive power are controlled. In fig. 5(b), phi is the impedance angle of the connecting reactor, and delta is the phase difference between the SVG output voltage Uc and the grid voltage Us. When the current leads the voltage of the power grid by 90 degrees, the SVG absorbs inductive reactive power; when the current lags the voltage of the power grid by 90 degrees, the SVG absorbs capacitive reactive power. Considering that the power grid provides active power for system loss, the phase difference between the power grid voltage Us and the current Ic is slightly smaller than 90 degrees, and the deviation angle is delta, namely the phase difference between the SVG output voltage Uc and the power grid voltage Us.
Fig. 6 shows a power decoupling equivalent control block diagram of three-level SVG in the apparatus of the present invention. The control mode of the SVG is a current indirect control method, the SVG is treated as a voltage control current source, and the output voltage U of the SVG is changedcIndirectly controlling SVG to absorb current I from power grid by phase and amplitudecIncluding a reactive current IcqIcq and active current IcdAnd the linear relation is respectively formed with the reactive power and the active power absorbed by the SVG. The method is through PIThe regulator realizes the decoupling of the reactive power module and the active power module, is simple to realize and has good dynamic response. As shown in fig. 5, in order to make the total voltage V on the DC sidedcKeeping constant, and comparing the reference value of the DC side voltage
And actually detecting the instantaneous value V of the DC side voltagedcThe difference value of the input active current is obtained through a PI regulator
And stabilizing the total voltage on the direct current side by controlling the active power absorbed by the SVG.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments thereof, and it is not intended to limit the practice of the invention to those embodiments, and in particular, to provide consistent results in other ways of adjusting the structure of the apparatus. For those skilled in the art to which the invention pertains, several equivalent substitutions or obvious modifications, which are equivalent in performance or use, should be considered to fall within the scope of the present invention without departing from the spirit of the invention.
Claims (8)
1. The utility model provides a be applied to intelligent integrated distribution device in low-voltage transformer district, the device connects in parallel on female the arranging of distribution network power supply, and the device includes SVG, intelligent capacitor bank and other switch circuit, control circuit for the unbalanced three phase and the idle hybrid compensation to the distribution network, thereby improve distribution network power quality, reduce system's cost.
2. The device of claim 1, wherein the SVG is connected in parallel to a power supply bus bar of the power distribution network, so as to adjust three-phase load imbalance and dynamically, bidirectionally and continuously adjust reactive power; the intelligent capacitor bank is connected in parallel to the power supply busbar of the power distribution network, so that three-phase load imbalance can be adjusted, and reactive power is compensated; and the SVG and the intelligent capacitor cooperate to jointly complete reactive compensation of the three-phase unbalanced load.
3. The device as claimed in claim 1 or 2, wherein the SVG is of modular design, the topology is three-level, the module may contain soft power-up circuit, energy storage unit, filter circuit, detection circuit, IGBT power conversion unit, driving circuit, tracking control circuit, auxiliary power system, monitor display liquid crystal screen, etc., and the energy storage unit uses capacitance or inductance element.
4. The apparatus of claim 1 or 2, wherein the intelligent capacitor bank is composed of a plurality of groups of intelligent capacitors, and the intelligent capacitor bank can be composed of a plurality of capacitor combinations of co-complement, sub-complement and hybrid complement. Each intelligent capacitor consists of a switching switch module and a capacitor group, wherein the switching switch module consists of a thyristor, a magnetic latching relay, a zero-crossing trigger conduction circuit and a thyristor protection circuit, so that zero switching of the capacitor is realized, and inrush current impact and operation overvoltage are avoided in the switching process. The switch module has high action response speed and can be frequently operated.
5. The device as claimed in any one of claims 1-4, wherein the SVG controller controls the on-off of the intelligent capacitor at the same time, the communication between the two is carried out through the RS485 interface, the switching of the intelligent capacitor is controlled through the SVG control chip, the switching compensation of the intelligent capacitor is preferentially controlled, and then the fine compensation and the three-phase unbalance compensation are carried out by adopting the SVG.
6. A method for achieving reactive compensation of a three-phase unbalanced load using an arrangement according to any of claims 1-5, characterized by the steps of: the system collects the voltage and current signals of the power grid and the load end in real time through the sensor, transmits the signals to the DSP through the signal conditioning circuit, performs reactive current calculation and reactive power distribution, obtains the switching scheme and SVG current control instructions of the intelligent capacitors, transmits the instructions to each intelligent capacitor through RS485 communication, controls the on-off of the capacitors, generates PWM control signals to drive the IGBTs in the SVG module, and finally completes reactive power compensation of three-phase unbalanced load through the cooperation of the two.
7. The method of claim 6, wherein the device controls the intelligent capacitor through the SVG internal controller to realize reactive compensation of the three-phase unbalanced load, and the method comprises the following steps:
(1) collecting system alternating current, sending the conditioned system alternating current to a DSP (digital signal processor) for coordinate transformation, decomposing to obtain three-phase fundamental wave positive sequence active current and other current components including the sum of harmonic wave, fundamental wave reactive current and fundamental wave negative sequence current, and separating reactive current; calculating the average current and obtaining the reactive current to be compensated;
(2) calculating the type and the number of intelligent capacitors to be switched according to a reactive power distribution principle, and controlling the on-off of thyristors of the corresponding intelligent capacitors in an RS485 communication mode to realize the switching of the intelligent capacitors;
(3) the intelligent capacitor also detects voltage and current signals of a power grid, collected data are calculated and analyzed to judge whether faults such as overcurrent, overvoltage and overheating occur, the working capacitor is cut off in time, and a main circuit is protected.
8. The method as claimed in claim 6 or 7, wherein SVG is controlled by DSP in the device to realize reactive compensation of three-phase unbalanced load, and the method comprises the following steps:
(1) collecting the voltage of a direct current bus of the system, sending the voltage into a DSP (digital signal processor) for conditioning, then carrying out PI (proportional integral) conditioning on the voltage and a reference value, and finally superposing the voltage and the reference value to a current detection instruction signal to finally realize the stable adjustment of the direct current bus;
(2) calculating a reactive current value needing SVG compensation by combining the reactive current component obtained by sampling calculation and the compensated reactive current of the intelligent capacitor;
(3) setting the SVG current compensation quantity to be opposite in polarity and equal in magnitude to the reactive current value to be compensated of the SVG, and controlling the total reactive current to be 0 by the compensation quantity and the reactive current component through a current regulator;
(4) and intersecting the output of the current regulator and the output of the triangular wave generator to obtain a PWM driving signal, and driving the corresponding IGBT module through the isolation amplifier.
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| CN112366716A (en) * | 2020-10-28 | 2021-02-12 | 广东电网有限责任公司韶关供电局 | Voltage balance system of low-voltage transformer area |
| CN112491060A (en) * | 2020-11-20 | 2021-03-12 | 青岛鼎信通讯股份有限公司 | Power factor management method based on linear variable relation recognition device |
| CN112531886A (en) * | 2020-10-26 | 2021-03-19 | 国网内蒙古东部电力有限公司电力科学研究院 | Power distribution station area mobile monitoring platform device, system and method |
| CN112531733A (en) * | 2020-12-30 | 2021-03-19 | 温州雅麦柯自动化科技有限公司 | SVG and silicon controlled rectifier reactive compensation complex mixed type reactive compensation system |
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| CN113922387A (en) * | 2021-10-14 | 2022-01-11 | 贵州电网有限责任公司 | Based on portable reactive power compensator in modularization low-voltage transformer district |
| CN116760055A (en) * | 2023-06-07 | 2023-09-15 | 东南大学 | Dynamic reactive compensation method based on neural network |
| CN117691610A (en) * | 2024-02-04 | 2024-03-12 | 东北电力大学 | Energy characteristic analysis method for AC/AC hybrid distribution transformer |
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